It is important for search engines to match user expectations. When executed in its original form, a search query submitted by a user may not retrieve all of the relevant documents or item listings. For example, the search query “earphones” may not return results for “earbuds,” even though the two queries are related to each other.
There are many reasons for a search engine being unable to match a user's expectations for a search query. Some reasons include differences in language models (e.g., “color” in American English versus “colour” in British English), acronym/abbreviation issues (e.g., “PS3” and “PlayStation 3”), spacing issues (“J crew” and “Jcrew”), synonym issues (e.g., “wedding dress” and “bridal gown”), and stemming issues (e.g., “van” and “Vans”).